CHARACTERISTIC DEEP-SEA TYPES. — SEA-URCHINS. 99 
The genus Rhynchopygus appeared at the time of the chalk, 
and is an interesting West Indian type. It is found on both 
sides of the Isthmus of Panama, and is characteristic of a period 
when there was a direct connection between the Caribbean Sea 
and the Bay of Panama. 
The allied Neolampas has no fossil representative. The allies 
of Conolampas date back to the cretaceous period. Conolampas 
Sigsbei (Fig. 368) is by far the most striking sea-urchin I have 
seen. I shall always remember the particular haul, on the edge 
of the Yucatan Bank, when the dredge came up containing half 
Fig. 368. — Conolampas Sigsbei. 1. 
a dozen of these huge brilliant lemon-colored echini. This mag- 
nificent species was originally referred to the fossil. genus Cono- 
elypus ; but Zittel having discovered that some species of this 
genus possessed teeth, De Loriol made an examination of the 
genus, and found that it really contained two generic types, one 
edentate, the other provided with teeth. These discoveries led 
me to make a renewed examination of Conoclypus Sigsbei. 
On opening a‘ specimen I found that it was edentate. This 
structural feature is most interesting, as it seems to show us the 
direct passage, as it were, between the edentate echini and those 
provided with teeth. 
Another typical genus from the chalk represented among the 
